104 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



VI. DETECTION OF OXALIC ACID. 



Evaporate 500 cc. of unfiltered urine over a small free 

 flame to about 150 cc. After cooling add 20 cc. of hydro- 

 chloric acid, transfer to a separating-funnel and shake with 

 about an equal volume of a mixture of alcohol and ether (9 

 volumes of ether ; 1 volume of absolute alcohol), carefully 

 separate the ether extract and filter it through a dry filter. 

 Repeat the extraction with ether once more and distil the 

 combined ether extracts from a dry flask. The fluid remain- 

 ing in the flask is poured into a dish, the flask being rinsed 

 out once with a little alcohol, then with water, and the mix- 

 ture is heated on the water-bath with the addition of some 

 water until the odor of alcohol and ether has disappeared. 

 The aqueous fluid remaining, whose volume should be about 

 20 cc., is cooled, and filtered from some resinous material 

 which separates. Make the solution faintly alkaline with 

 ammonia, add 1 or 2 cc. of a 10 per cent, calcium chloride 

 solution, and acidify with acetic acid. The white precipitate 

 of calcium oxalate, which forms either at once or else gradu- 

 ally, is amorphous, but quite homogeneous when it separates 

 quickly. It is crystalline when precipitated more slowly, 

 and then frequently shows, instead of octahedral forms, those 

 described by Feser and Friedberger 1 (quadratic prisms with 

 pyramidal end faces). 



VII. HIPPURIC ACID, BENZOYL GLYCOCOLL, 

 CH 2 NH(COC 6 H 5 ) 



COOH 



To about 300 cc. of horse-urine add milk of lime till the 

 reaction is strongly alkaline (to separate phosphoric acid 

 and a part of the coloring matter), filter, evaporate to sirupy 



1 Maly's Jahresber. f. Thierchemie, 4, 231. 



